Aptitude - Logarithm

Exercise :: Logarithm - General Questions

11. 

If log 2 = 0.30103, the number of digits in 264 is:

A. 18
B. 19
C. 20
D. 21

Answer: Option C

Explanation:

log (264) = 64 x log 2
= (64 x 0.30103)
= 19.26592

Its characteristic is 19.

Hence, then number of digits in 264 is 20.


12. 

If logx 9 = - 1 , then x is equal to:
16 2

A.
- 3
4
B.
3
4
C.
81
256
D.
256
81

Answer: Option D

Explanation:

logx 9 = - 1
16 2

x-1/2 = 9
16

1 = 9
x 16

x = 16
9

x = 16 2
9

x = 256
81


13. 

If ax = by, then:

A.
log a = x
b y
B.
log a = x
log b y
C.
log a = y
log b x
D. None of these

Answer: Option C

Explanation:

ax = by

log ax = log by

x log a = y log b

log a = y .
log b x


14. 

If logx y = 100 and log2 x = 10, then the value of y is:

A. 210
B. 2100
C. 21000
D. 210000

Answer: Option C

Explanation:

log 2 x = 10         x = 210.

logx y = 100

y = x100

y = (210)100     [put value of x]

y = 21000.


15. 

The value of log2 16 is:

A.
1
8
B. 4
C. 8
D. 16

Answer: Option B

Explanation:

Let log2 16 = n.

Then, 2n = 16 = 24         n = 4.

log2 16 = 4.


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